Approximately 3% of circulating human platelets, representing the tissues most recently released by megakaryocytes, contain mRNA. Platelets contain mRNA for m-calpain, mu-calpain, calpastatin, and the 5HT2a receptor. All of these proteins are involved in a calcium-based signaling pathway. Having established that certain calcium-related signal transduction proteins appear to be modulated by ethanol exposure in PC12 cells, we are interested in examining whether the level of gene expression in human platelets changes in parallel fashion as that observed in cell culture, during and after exposure to ethyl alcohol. Our preliminary work was carried out using outdated human platelets. A method was developed, based on RT-PCR, to quantitatively measure the levels of expression for target genes of interest using relatively small quantities of blood (approximately 1 ml). The methodology will be used to probe gene expression in platelets obtained from subjects admitted to our inpatient unit for alcohol detoxification. By sampling the subjects throughout the period of admission, we hope to determine whether significant changes in message occur over time, while relating such changes to relevant demographic parameters, historical data relevant to ethanol consumption, and level of alcohol withdrawal symptoms.